Do you know what pruning is? Did you know that there are two main styles of pruning winegrapes?
Ryan Decker, our Wine Grower Relations Manager, gives us insight into the who, what, where, when and why we prune the vineyards every winter:
It’s depressing, really.
After the leaves that worked to ripen our vintage this year fall to the ground to provide nutrients for future crops, we begin the barbaric ritual of vine mutilation – aka pruning. After all, these are vines. Left to their own devices, they would probably climb up and take over every standing structure on the planet if given enough time. So we must valiantly fight the vines if humankind is to survive. But seriously, pruning is one of the most important concepts in viticulture, second only to irrigation. By removing wood from the vine we are altering its future shape, size, potential yield, vigor, and even health.
There are really only two styles of pruning winegrapes – cane and spur. Cane pruning normally utilizes long bearing canes, usually 10-15 buds in length, derived from last year’s green shoots. These canes are tied horizontally to wires, and will grow green shoots in the spring that will bear the crop for the upcoming harvest. These canes are accompanied by 2-bud renewal spurs that will produce the following year’s canes. Spur pruning involves the removal of all previous year’s growth except for a number of ‘two-bud spurs’ spaced evenly along a horizontal trunk, called a cordon. The highly technical method of determining the ideal spacing between spurs requires a fist and a pruning shear. The spurs should be no closer together than your fist, and no further apart than your pruning shear. Of course, this rule does not apply if you happen to be using loppers. The proper spacing of spurs makes other cultural practices, like shoot thinning and leaf pulling, easier to accomplish down the road.
The concept of vine balance is somewhat of a moving target, but it is generally accepted that each site has a theoretical maximum yield that can be achieved before quality begins to be impacted. One of the most useful measurements used to track vine balance is the yield:pruning weight ratio, known as the Ravaz index. This is a fairly simple way to determine if the vines are under- or over-cropped. The ideal range for North Coast vineyards is somewhere between 5:1 and 8:1. If the ratio is over 8:1, the vine should be pruned more severely because it is hanging too much fruit and quality is suffering. If the ratio is under 5:1, the vine is too vigorous and pruning should be less severe to encourage more shoots with a larger crop.
Even if a vineyard is pruned to perfection, it is up to the management team to maintain vineyard balance through the judicious use of water, pesticides and fertilizer, and the timely implementation of cultural practices. The next time you see a tidy, uniform vineyard with its perfect rows and flowering cover crop, just know that it is only a few cuts away from taking over the world!